From the New York Times, 9/6/1879

The burning down of the notorious
military prison, popularly known as Castle Thunder, in Richmond,
Va., the other day, removes another of the monuments of the civil
war. It stood but a little distance from Libby Prison, and, like it,
was originally a tobacco factory. A number of the Union officers
were confined there on special charges, as were several of the war
correspondents of the New York newspapers, who were held, so the
rebels absurdly put it, as hostages for the good conduct of the
Government. It was used generally, however, for the confinement of
Southern citizens who had been suspected of the crime of Unionism,
and of rebel officers who had been accused of violating military
laws. Two or three Union men were hanged as spies in the inclosure
of the prison, and many thrilling scenes of daring and escape were
enacted there during the eventful four years of the bloody struggle.
The prisoners were often brutally and cruelly treated, especially by
Capt. ALEXANDER, of Baltimore, for some time keeper of the horrid
den. Castle Thunder has a strange and romantic, as well as horrible
history, which was never been half written, and which is not now
likely to be. The old smoke-begrimed walls, still standing, have
witnessed great suffering and the slow agony of many a poor soul.